Problem with POST URLConnection

When I send a parameter through POST to a URL, I'm redirected to another URL, it's redirecting me to the right URL, but it returns me:

<script LANGUAGE=JavaScript>alert('Seu tempo expirou. Por favor entre novamente');location.href='logon.asp';</script>

My Activity Code:

public class HttpPostAsyncTask extends AsyncTask<String,Void,String> {
    @Override
    protected String doInBackground(String... param) {

        content = new StringBuilder();
        String response= "";

        try {

            URL link = new URL(url+path);
            HttpURLConnection.setFollowRedirects(true);
            HttpURLConnection conn = (HttpURLConnection) link.openConnection();
            conn.setInstanceFollowRedirects(true);
            conn.setDoOutput(true);
            conn.setRequestMethod("POST");
            conn.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");

            String charset = "UTF-8";
            String s = "txtnumero_matricula=" + URLEncoder.encode(login, charset);
            s += "&txtsenha_tac=" + URLEncoder.encode(senha, charset);
            s += "&cmdEnviar=" + URLEncoder.encode(param, charset);

            conn.setFixedLengthStreamingMode(s.getBytes().length);
            PrintWriter out = new PrintWriter(conn.getOutputStream());
            out.print(s);
            out.close();

            System.out.print(conn.getURL());

            conn.connect();

            Scanner inStream = new Scanner(conn.getInputStream());

            while(inStream.hasNextLine())
                response += (inStream.nextLine());

                System.out.println(conn.getURL()+"  "+response);

        } catch (ProtocolException e1) {
            e1.printStackTrace();
        } catch (UnsupportedEncodingException e1) {
            e1.printStackTrace();
        } catch (IOException e1) {
            e1.printStackTrace();
        }
        return response.toString();
    }

    @Override
    protected void onPostExecute(String html) {
        super.onPostExecute(html);

    }
}

I made more tests and any parameter that I sent, right or wrong, it returns the same SCRIPT.